arXiv subjects

Theodore Andronikos

Publications and source records attributed to Theodore Andronikos.

At least 19 recordsLinked to original sources

arXiv2026

AI-Farol: Co-Evolutionary Dynamics in a Multi-Agent Two-Sided Learning Framework

The El Farol Bar game is a classical model of coordination under uncertainty that traditionally treats the venue as a passive constraint. In this work, we reconceptualize the problem by modeling the bar as a strategic player endowed with AI-driven learning capabilities. We extend the original framework in two principal directions: first, by introducing partial observability, whereby agents observe only subsets of past attendees; and second, by transforming the bar from a passive capacity threshold into an active mechanism designer that adjusts pricing policies to balance revenue, utilization, and sustainability constraints. Agents employ AI-based learning to form beliefs and adapt attendance strategies under incomplete information, while the bar applies policy learning to optimize dynamic pricing. The resulting two-sided learning system frames coordination as a co-evolutionary process between boundedly rational agents and an adaptive institution, offering insights into congestion management, resource allocation, and mechanism design in complex adaptive systems.

cs.GT↗

arXiv2026

Evaluation of Variational Quantum Classifiers (VQC) for Cyberattack Detection in the NISQ Era

This paper investigates the effectiveness and structural limits of Variational Quantum Classifiers (VQC) for detecting network anomalies in the era of Noisy Intermediate-Scale Quantum (NISQ) systems. Using the official 20\% research subset of the NSL-KDD dataset, a 4-qubit classifier featuring a 24-parameter trainable ansatz was developed, utilizing amplitude encoding to embed 16 principal components. On a held-out partition of this subset, the model achieved a consistent binary-classification accuracy of 88\%. A comparative evaluation with two fundamentally different optimizers, COBYLA and SPSA, found that the observed performance plateau is not attributable to convergence to local minima, a result we interpret as consistent with an encoding-related expressibility limit rather than an optimization artifact. An architectural parity comparison with a classical neural network (a Tiny MLP with four nodes, achieving 97\% accuracy) highlighted the expressiveness gap associated with data overcompression into restricted quantum states. The model was trained on a class-balanced set spanning the 22 raw NSL-KDD attack categories and evaluated in-sample as a probe of representational capacity: under this configuration the VQC reached only 9\% accuracy and exhibited a degenerate mode collapse onto a small subset of classes. We interpret this behavior as consistent with the loss of linear separability induced by excessive compression in the quantum probability space, while explicitly noting that our experiments do not isolate the encoding from the ansatz depth, optimizer budget, and measurement-decoding scheme (see Limitations). Motivated by these observations and by Cover's theorem, we outline an alternative paradigm: a 16-qubit VQC with angle encoding that expands the Hilbert-space representation rather than relying on aggressive classical dimensionality reduction.

quant-ph↗

arXiv2026

Extending the El Farol Bar Game with Partial Observability and Incentive Design

The El Farol Bar game is a classic model of coordination under uncertainty, traditionally treating the venue as a passive constraint. In this work, we re-conceptualize the problem by modeling the bar as a strategic player equipped with AI-driven learning capabilities. We extend the original framework to include partial observability, i.e., agents observe only subsets of past attendees, and transform the bar from a passive capacity threshold into an active mechanism designer that adjusts pricing policies to balance revenue, utilization, and sustainability constraints. Agents employ AI-based learning to form beliefs and adapt attendance strategies under incomplete information, while the bar uses policy learning to optimize dynamic pricing. The resulting two-sided learning system frames coordination as a co-evolutionary process between boundedly rational agents and an adaptive institution, offering insights into congestion management, resource allocation, and mechanism design in complex adaptive systems.

cs.GT↗

arXiv2025

Probabilistic Links Between Quantum Classification of Patterns of Boolean Functions and Hamming Distance

This article investigates the probabilistic relationship between quantum classification of Boolean functions and their Hamming distance. By integrating concepts from quantum computing, information theory, and combinatorics, we explore how Hamming distance serves as a metric for analyzing deviations in function classification. Our extensive experimental results confirm that the Hamming distance is a pivotal metric for validating nearest neighbors in the process of classifying random functions. One of the significant conclusions we arrived is that the successful classification probability decreases monotonically with the Hamming distance. However, key exceptions were found in specific classes, revealing intra-class heterogeneity. We have established that these deviations are not random but are systemic and predictable. Furthermore, we were able to quantify these irregularities, turning potential errors into manageable phenomena. The most important novelty of this work is the demarcation, for the first time to the best of our knowledge, of precise Hamming distance intervals for the classification probability. These intervals bound the possible values the probability can assume, and provide a new foundational tool for probabilistic assessment in quantum classification. Practitioners can now endorse classification results with high certainty or dismiss them with confidence. This framework can significantly enhance any quantum classification algorithm's reliability and decision-making capability.

quant-ph↗

arXiv2025

Quantum Shadows: The Dining Information Brokers

This article introduces the innovative Quantum Dining Information Brokers Problem, presenting a novel entanglement-based quantum protocol to address it. The scenario involves $n$ information brokers, all located in distinct geographical regions, engaging in a metaphorical virtual dinner. The objective is for each broker to share a unique piece of information with all others simultaneously. Unlike previous approaches, this protocol enables a fully parallel, single-step communication exchange among all brokers, regardless of their physical locations. A key feature of this protocol is its ability to ensure both the anonymity and privacy of all participants are preserved, meaning no broker can discern the identity of the sender behind any received information. At its core, the Quantum Dining Information Brokers Problem serves as a conceptual framework for achieving anonymous, untraceable, and massively parallel information exchange in a distributed system. The proposed protocol introduces three significant advancements. First, while quantum protocols for one-to-many simultaneous information transmission have been developed, this is, to the best of our knowledge, one of the first quantum protocols to facilitate many-to-many simultaneous information exchange. Second, it guarantees complete anonymity and untraceability for all senders, a critical improvement over sequential applications of one-to-many protocols, which fail to ensure such robust anonymity. Third, leveraging quantum entanglement, the protocol operates in a fully distributed manner, accommodating brokers in diverse spatial locations. This approach marks a substantial advancement in secure, scalable, and anonymous communication, with potential applications in distributed environments where privacy and parallelism are paramount.

quant-ph↗

arXiv2025

Quantum Classification Outside the Promised Class

This paper studies the important problem of quantum classification of Boolean functions from a entirely novel perspective. Typically, quantum classification algorithms allow us to classify functions with a probability of $1.0$, if we are promised that they meet specific unique properties. The primary objective of this study is to explore whether it is feasible to obtain any insights when the input function deviates from the promised class. For concreteness, we use a recently introduced quantum algorithm that is designed to classify with probability $1.0$ using just a single oracular query a large class of imbalanced Boolean functions. Fist, we establish a completely new concept characterizing ``nearness'' between Boolean function. Utilizing this concept, we show that, as long as the input function is close enough to the promised class, it is still possible to obtain useful information about its behavioral pattern from the classification algorithm. In this regard, the current study is among the first to provide evidence that shows how useful it is to apply quantum classification algorithms to functions outside the promised class in order to get a glimpse of important information.

quant-ph↗

arXiv2025

A Quantum Algorithm for the Classification of Patterns of Boolean Functions

This paper introduces a novel quantum algorithm that is able to classify a hierarchy of classes of imbalanced Boolean functions. The fundamental characteristic of imbalanced Boolean functions is that the proportion of elements in their domain that take the value $0$ is not equal to the proportion of elements that take the value $1$. For every positive integer $n$, the hierarchy contains a class of Boolean functions defined based on their behavioral pattern. The common trait of all the functions belonging to the same class is that they possess the same imbalance ratio. Our algorithm achieves classification in a straightforward manner as the final measurement reveals the unknown function with probability $1$. Let us also note that the proposed algorithm is an optimal oracular algorithm because it can classify the aforementioned functions with a single query to the oracle. At the same time we explain in detail the methodology we followed to design this algorithm in the hope that it will prove general and fruitful, given that it can be easily modified and extended to address other classes of imbalanced Boolean functions that exhibit different behavioral patterns.

quant-ph↗

arXiv2024

A distributed and parallel $(k, n)$ QSS scheme with verification capability

This article introduces a novel Quantum Secret Sharing scheme with $( k, n )$ threshold and endowed with verification capability. The new protocol exploits the power of entanglement and evolves in three phases. The primary novelty of the new protocol lies in its ability to operate completely parallelly in a fully distributed setup, where the spymaster and her agents all are in different locations, in contrast to the vast majority of analogous protocols that assume a localized scenario in which all agents are at the same place. The spymaster sends all necessary information to all intended recipients simultaneously in one step. All phases are executed in parallel, minimizing the overall execution cost of the protocol. Given its comparative complexity, we provide a comprehensive and detailed analysis to establish its information-theoretic security in the sense of preventing both outside eavesdroppers from obtaining any useful information and inside rogue agents from sabotaging its successful completion. The protocol eliminates the need for a quantum signature scheme or pre-shared keys, thereby simplifying the process and lowering complexity. Finally, the possibility of its implementation by contemporary quantum computers is promising because the protocol relies exclusively on CNOT and Hadamard gates and all players operating on similar or identical quantum circuits.

quant-ph↗

arXiv2024

A Multiparty Quantum Private Equality Comparison scheme relying on $\ket{ GHZ_{ 3 } }$ states

This paper introduces an innovative entanglement-based protocol that accomplishes multiparty quantum private comparison leveraging maximally entangled GHZ3 triplets. The primary motivation is the design of a protocol that can be executed by contemporary quantum computers. This is made possible because the protocol uses only GHZ3 triplets, irrespective of the number of millionaires. While more complex multi-particle entangled states are possible, they are challenging to produce with existing quantum apparatus, leading to extended preparation time and complexity, particularly in scenarios involving numerous participants. By relying on GHZ3 states, which are the easiest to produce after Bell states, we avoid these drawbacks, and take a step towards the practical implementation of the protocol. An important quantitative characteristic of this protocol is that the required quantum resources are linear both in the number of millionaires and the volume of information to be compared. A notable aspect of the protocol is its suitability for both parallel and sequential execution. Although the execution of the quantum part of the protocol is envisioned to take place completely in parallel, it is also possible to be implemented sequentially. So, if the quantum resources do not suffice for the execution of the protocol in one go, it is possible to partition the millionaires into smaller groups and process these groups sequentially. Notably, our protocol involves two third parties; Trent is now accompanied by Sophia. This dual setup allows simultaneous processing of all n millionaires' fortunes. Implementation-wise, uniformity is ensured as all millionaires use similar private quantum circuits composed of Hadamard and CNOT gates. Lastly, the protocol is information-theoretically secure, preventing outside parties from learning about fortunes or inside players from knowing each other's secret numbers.

quant-ph↗

arXiv2024

A Quantum Approach to News Verification from the Perspective of a News Aggregator

In the dynamic landscape of digital information, the rise of misinformation and fake news presents a pressing challenge. This paper takes a completely new approach to verifying news, inspired by how quantum actors can reach agreement even when they are spatially spread out. We propose a radically new, to the best of our knowledge, algorithm that uses quantum ``entanglement'' (think of it as a special connection) to help news aggregators sniff out bad actors, whether they be other news sources or even fact-checkers trying to spread misinformation. This algorithm doesn't rely on quantum signatures, it just uses basic quantum technology we already have, in particular, special pairs of particles called ``EPR pairs'' that are much easier to create than other options. More complex entangled states are like juggling too many balls - they're hard to make and slow things down, especially when many players are involved. For instance, bigger, more complex states like ``GHZ states'' work for small groups, but they become messy with larger numbers. So, we stick with Bell states, the simplest form of entanglement, which are easy to generate no matter how many players are in the game. This means our algorithm is faster to set up, works for any number of participants, and is more practical for real-world use. Bonus points: it finishes in a fixed number of steps, regardless of how many players are involved, making it even more scalable. This new approach may lead to a powerful and efficient way to fight misinformation in the digital age, using the weird and wonderful world of quantum mechanics.

quant-ph↗

arXiv2024

A Novel Scalable Quantum Protocol for the Dining Cryptographers Problem

This paper presents an innovative entanglement-based protocol to address the Dining Cryptographers Problem, utilizing maximally entangled $\ket{ GHZ_{ n } }$ tuples as its core. This protocol aims to provide scalability in terms of both the number of cryptographers $n$ and the amount of anonymous information conveyed, represented by the number of qubits $m$ within each quantum register. The protocol supports an arbitrary number of cryptographers $n$, enabling scalability in both participant count and the volume of anonymous information transmitted. While the original Dining Cryptographers Problem focused on a single bit of information, i.e., whether a cryptographer paid for dinner, the proposed protocol allows $m$, the number of qubits in each register, to be any arbitrarily large positive integer. This flexibility permits the conveyance of various information, such as the cost of the dinner or the timing of the arrangement. Another noteworthy aspect of the introduced protocol is its versatility in accommodating both localized and distributed versions of the Dining Cryptographers problem. The localized scenario involves all cryptographers gathering physically at the same location, such as a restaurant, simultaneously. In contrast, the distributed scenario accommodates cryptographers situated in different places, engaging in a virtual dinner at the same time. Finally, in terms of implementation, the protocol ensures uniformity by requiring all cryptographers to utilize identical private quantum circuits. This design establishes a completely modular quantum system where all modules are identical. Furthermore, each private quantum circuit exclusively employs the widely used Hadamard and CNOT quantum gates, facilitating straightforward implementation on contemporary quantum computers.

quant-ph↗

arXiv2023

One-to-Many Simultaneous Secure Quantum Information Transmission

This paper presents a new quantum protocol designed to simultaneously transmit information from one source to many recipients. The proposed protocol, which is based on the phenomenon of entanglement, is completely distributed and is provably information-theoretically secure. Numerous existing quantum protocols guarantee secure information communication between two parties but are not amenable to generalization in situations where the source must transmit information to two or more parties, so they must be applied sequentially two or more times in such a setting. The main novelty of the new protocol is its extensibility and generality to situations involving one party that must simultaneously communicate different, in general, messages to an arbitrary number of spatially distributed parties. This is achieved by the special way employed to encode the transmitted information in the entangled state of the system, one of the distinguishing features compared to previous protocols. This protocol can prove expedient whenever an information broker, say, Alice, must communicate distinct secret messages to her agents, all in different geographical locations, in one go. Due to its relative complexity, compared to similar cryptographic protocols, as it involves communication among $n$ parties, and relies on $GHZ_{n}$ tuples, we provide an extensive and detailed security analysis so as to prove that it is information-theoretically secure. Finally, in terms of its implementation, the prevalent characteristic of the proposed protocol is its uniformity and simplicity because it only requires CNOT and Hadamard gates, and the local quantum circuits are identical for all information recipients.

quant-ph↗

arXiv2023

Quantum Tapsilou -- a quantum game inspired from the traditional Greek coin tossing game tapsilou

This paper introduces a new quantum game called Quantum Tapsilou that is inspired by the classical traditional Greek coin tossing game tapsilou. The new quantum game, despite its increased complexity and scope, retains the most important characteristic of the traditional game. In the classical game, both players have $\frac { 1 } { 4 }$ probability to win. The quantum version retains this characteristic feature, that is both players have the same probability to win, only now this probability varies considerably and depends on previous moves and choices. The two most important novelties of Quantum Tapsilou can be attributed to its implementation of entanglement via the use of rotation gates instead of Hadamard gates, which generates Bell-like states with unequal probability amplitudes, and the integral use of groups. In Quantum Tapsilou both players agree on a specific cyclic rotation group of order $n$, for some sufficiently large $n$. The game is based on the chosen group, in the sense that both players will draw their moves from its elements. More specifically, both players will pick rotations from this group to realize their actions using the corresponding $R_{ y }$ rotation gates. In the Quantum Tapsilou game, it is equally probable for both players to win. This fact is in accordance with a previous result in the literature showing that quantum games where both players choose their actions from the same group, exhibit perfect symmetry by providing each player with the possibility to pick the move that counteracts the other player's action.

quant-ph↗

arXiv2023

A novel $2$ \& $3$ player scheme for Quantum Direct Communication

This paper introduces two information-theoretically secure protocols that achieve quantum secure direct communication between Alice and Bob in the first case, and among Alice, Bod and Charlie in the second case. Both protocols use the same novel method to embed the secret information in the entangled compound system. The way of encoding the information is the main novelty of this paper and the distinguishing feature compared to previous works in this field. The most critical advantage of this method is that it is easily scalable and extensible because it can be seamlessly generalized to a setting involving three, or even more, players, as demonstrated with the second protocol. This trait can be extremely beneficial when many spatially separated players posses only part the secret information that must be combined and transmitted to Alice, so that she can obtain the complete secret. Using the three player protocol, this task can be achieved in one go, without the need to apply a typical QSDC protocol twice, where Alice first receives Bob's information and afterwards Charlie's information. The proposed protocol doesn't require pre-shared keys or quantum signatures, making it less complicated and more straightforward. Finally, by employing only standard CNOT and Hadamard gates, it offers the important practical advantage of being implementable on contemporary quantum computers, especially in view of the coming era of quantum distributed computing.

quant-ph↗

arXiv2023

A Quantum Detectable Byzantine Agreement Protocol using only EPR pairs

In this paper, we introduce a new quantum protocol for Detectable Byzantine Agreement. What distinguishes the proposed protocol among similar quantum protocols, is the fact that it uses only EPR pairs, and, in particular, $\Psi^{ + }$ pairs. There are many sophisticated quantum protocols that guarantee Detectable Byzantine Agreement, but they do not easily lend themselves to practical implementations, due to present-day technological limitations. For a large number $n$ of players, GHZ $n$-tuples, or other more exotic entangled states, are not easy to produce, a fact which might complicate the scalability of such protocols. In contrast, Bell states are, undoubtedly, the easiest to generate among maximally entangled states. This will, hopefully, facilitate the scalability of the proposed protocol, as only EPR pairs are required, irrespective of the number $n$ of players. Finally, we mention that, even for arbitrary many players $n$, our protocol always completes in a constant number of rounds, namely $4$.

quant-ph↗

arXiv2023

An entanglement-based protocol for simultaneous reciprocal information exchange between 2 players

Let us consider a situation where two information brokers, whose currency is, of course, information, need to reciprocally exchange information. The two brokers, being somewhat distrustful, would like a third, mutually trusted, entity to be involved in the exchange process so as to guarantee the successful completion of the transaction, and also verify that it indeed took place. Can this be done in such a way that both brokers receive their information simultaneously and securely, and without the trusted intermediary ending up knowing the exchanged information? This work presents and rigorously analyzes a new quantum entanglement-based protocol that provides a solution to the above problem. The proposed protocol is aptly named entanglement-based reciprocal simultaneous information exchange protocol. Its security is ultimately based on the assumption of the existence of a third trusted party. Although, the reciprocal information flow is between our two information brokers, the third entity plays a crucial role in mediating this process, being a guarantor and a verifier. The phenomenon of quantum entanglement is the cornerstone of this protocol, as it makes possible its implementation even when all entities are spatially separated, and ensuring that, upon completion, the trusted third party remains oblivious of the actual information that was exchanged.

quant-ph↗

arXiv2022

Viewing biological and computer viruses as manifestations of games

Computer viruses exhibit many similarities with biological viruses. Thus, a closer examination of this association might lead to some new perspectives and, even, to new enhanced capabilities that will facilitate the overall effort to tackle and, why not, eradicate them. Game theory has long been considered as a useful tool for modeling viral behavior. In this paper, we establish certain, important we hope, correlations between a well-known virus, namely VirLock, with the bacteriophage $\phi6$. Moreover, following this line of thought, we also suggest efficient and, at the same time, practical strategies that may significantly alleviate the infection problems caused by VirLock and any other virus having similar traits.

cs.GT↗

arXiv2022

Quantum secret aggregation utilizing a network of agents

In this work we consider the following problem: given a network of spies, all distributed in different locations in space, and assuming that each spy possesses a small, but incomplete by itself part of a big secret, is it possible to securely transmit all these partial secrets to the spymaster, so that they can be combined together in order to reveal the big secret? We refer to it as the Quantum Secret Aggregation problem, and we propose a protocol, in the form of a quantum game, with Alice taking over the role of the spymaster, that addresses this problem in complete generality. Our protocol relies on the use of maximally entangled GHZ tuples, which are symmetrically distributed among Alice and all her spies. It is the power of entanglement that makes possible the secure transmission of the small partial secrets from the agents to the spymaster. As an additional bonus, entanglement guarantees the security of the protocol, by making it statistically improbable for the notorious eavesdropper Eve to steal the big secret.

quant-ph↗